<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>exchangeRate</title>

    <style>
        div{
            margin: 5px auto;
            /*margin-left: 100px;*/
            align-self: center;
            width: 500px;
        }
        table{
            width: 500px;
            border: 1px black solid;
            padding: 1px;
        }
        th,td{
            height: 35px;
            text-align: center;
            border: 1px black solid;
        }
        #headtext{
            background: red;
        }
    </style>
</head>
<body>
<div>
    <select name="" id="1">
        <option value="123">123</option>
        <option value="321">321</option>
    </select>
    <input type="submit" value="互换">
    <select name="" id="2">
        <option value="123">123</option>
        <option value="321">321</option>
    </select>
    数额:
    <input type="text" placeholder="123">
    <input type="submit" value="汇率转换">
</div>
<div>
    <table>
        <tr id="headtext">
            <th colspan="3">按当前汇率兑换结果</th>
        </tr>
        <tr>
            <td>1</td>
            <td>1</td>
            <td>1</td>
        </tr>
        <tr>
            <td>1</td>
            <td>1</td>
            <td>1</td>
        </tr>

    </table>
</div>
<div>

</div>
</body>
</html>